CrOS Shelf: When the hotseat is enabled, also enable scrollable shelf

Bug: 973481, 973482, 973483
Change-Id: I5e4a521508defaa48a7d62c26ade5d092b112b08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1797486Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697280}

chromeos/constants/chromeos_switches.cc

@@ -557,6 +557,9 @@ bool ShouldShowShelfHoverPreviews() {
 }
 
 bool ShouldShowScrollableShelf() {
+  // If we're showing the new shelf design, also enable scrollable shelf.
+  if (ShouldShowShelfHotseat())
+    return true;
   return base::CommandLine::ForCurrentProcess()->HasSwitch(kShelfScrollable);
 }